• Bulletin of the Korean Chemical Society
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• v.11 no.5
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• pp.455-460
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• 1990

2,5-Disubstituted tetrahydrofurans 11-13 were prepared by phenylselenoetherification of 1-alkyl-4-phenyl-(3E)-butenols 8-10 under kinetic conditions. Their stereochemical outcome and reactivity were controlled by solvent, reaction temperature and the alkyl substituent. While the cyclization was stereorandom in dichloromethane, its stereoinduction was moderate to good in propionitrile and good to excellent in diethyl ether. The reaction went to completion in dichloromethane and propionitrile, but it did not in diethyl ether. The results can be rationalized by the degree of reversibility in the formation of episelenonium cation and 1,3-diaxial interactions in the transition state of the formation of tetrahydrofuranonium cation.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.500-503
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• 1989

Synthetic studies have been carried out for the addition or substitution of phosphorus nucleophiles to the cation $[(exo-6-R-{\eta}^ {5_-}2-MeO-C_6H_5)Mn(CO)_2NO]PF_6,$ 2. $PPh_3$ reacts with 2 to yield the CO displaced product and $MePPh_2$ attacks the dienyl ring of 2 to yield the phosphonium adduct or the metal to give the CO displaced depending upon the reaction temperatures. Nucleophilic addition of HPPh2 to the dienyl ring of 2 gives a neutral substituted product. $P(OMe)_3$ reacts with 2 to yield a mixture of ring adduct and CO displaced product at room temperature. $At - 20^{\circ}C,\;P(OMe)_3$ attacks the dienyl ring of 2 to give a posphonium adduct, which underwent Arbuzov reaction. This reaction affords a new route to the phosphonate complexes.

• Bulletin of the Korean Chemical Society
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• v.19 no.12
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• pp.1355-1359
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• 1998

The treatment of 1,1-bis(phenylthio)-2,2,3,3,3-pentafluoropropylbenzene (1) with 2 equiv. of phenyllithium in THF at -78 ℃ resulted in the formation of isomeric mixture (70: 30) of trifluoromethylated 1,2-diphenylvinyl sulfide 2 in 87% yield. The further oxidation of 2 with m-chloroperbenzoic acid in methylene chloride afforded isomeric mixture (70:30) of trifluoromethylated 1,2-diphenylvinyl sulfone 3 in 87% yield. When 3 was reacted with carbon nucleophiles such as methyllithium, n-butyllithium, phenyllithium and lithium octylide, the corresponding addition-elimination adducts 4, 5, 6 and 7 were obtained in moderate to good yields. The reaction of 3 with 4 equiv. of tributyltin hydride in benzene at reflux temperature provided isomeric mixture (90 : 10) of trifluoromethylated 1,2-diphenylvinyl stannane 8 in 41% yield. The reaction of 8 with methyllithium in the presence of trimethylsilyl chloride gave isomeric mixtures (90: 10) of trifluoromethylated 1,2-diphenylvinyl silane 9 in 88% yield. Finally, the treatment of 8 with Br2 and 12 resulted in the formation of isomeric mixtures (90: 10) of trifluoromethylated 1,2-diphenylvinyl bromide 10 and iodide 11 in 72% and 90% yields, respectively.

• Bulletin of the Korean Chemical Society
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• v.19 no.5
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• pp.533-539
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• 1998

A magnetic film was deposited on a slide glass substrate from aqueous solutions of $FeCl_2$ and $NaNO_2$ at 363 K. XRD analysis showed that the film was polycrystalline magnetite $(Fe_{3(1-{\sigma})}O_4)$ without impurity phase. The lattice constant was 0.8390 nm. Mossbauer spectrum of the film could be deconvoluted by the following parameters: isomer shifts for tetrahedral $(T_d)$ and octahedral $(O_h)$ sites are 0.28 and 0.68 mm/s, respectively, and corresponding magnetic hyperfine fields are 490 and 458 kOe, respectively. The estimated chemical formula of the film by the peak intensity of Mossbauer spectrum was $Fe_{2.95}O_4$. Low temperature transition of the magnetite (Verwey transition) was not detected in resistivity measurement of the film. Properties of the film were discussed with those of pressed pellet and single crystal of synthetic magnetites. On the surface of the film, magnetite particles of about 0.2 μm in diameter were identified by noncontact atomic force microscopy (NAFM) and magnetic force microscopy (MFM).

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.826-831
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• 2019

Experimental data of phase equilibrium is reported for caprolactone acrylate in supercritical carbon dioxide. Bubble-point data was measured by synthetic method at temperatures ranging from (313.2 to 393.2) K and pressures up to 55.93 MPa. In this research, the solubility of carbon dioxide for the (carbon dioxide + caprolactone acrylate) system decreases as temperature increases at a constant pressure. The (carbon dioxide + caprolactone acrylate) system exhibits type-I phase behavior. The experimental result for the (carbon dioxide + caprolactone acrylate) system was correlated with Peng-Robinson equation of state using mixing rule. The critical property of caprolactone acrylate was predicted with the Joback and Lyderson method.

• YAKHAK HOEJI
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• v.56 no.6
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• pp.390-394
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• 2012

A series of new pyridazinyl sulfoxides 3a~e and pyridazinyl sulfones 4a were synthesized for development of candidates to retain anticancer activity. The utility of sulfoxides and sulfones in both laboratory and industrial practice was quickly recognized, and these species have been extensively utilized, including as pharmaceutical intermediates and anticancer agents. Alkylthiopyridazines 2a~e were prepared from the 3,6-dichloropyridazine using allylthiolation with alkyl mercaptan. Sulfides could be oxidized to sulfoxides or sulfones using 1~3 equivalents of hydrogen peroxide as an oxidant. The oxidation of sulfoxides to sulfones was also accomplished with aqueous hydrogen peroxide. Formation of 3a~e and 4a was undertaken with stirring using 35% hydrogen peroxide at room temperature in acetic acid for 18~72 h. Synthetic compounds were identified using NMR spectrum.

• The Korean Journal of Food And Nutrition
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• v.32 no.1
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• pp.41-49
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• 2019

Carotene, xanthophyll, carotenoid anthocyan, phycopyrine, chlorophyll, and monascus pigments are used as natural coloring agents since they are more stable to human body than synthetic coloring agents. Among them, monascus pigments are a natural red pigment produced by the Monascus purpureus. For the development of edible paint using natural pigment, Monascus purpureus strain was cultured at a temperature of $35^{\circ}C$ for 15 days on a PDYA plate and liquid medium to produce a red pigment. In addition, a large amount of the red pigment was extracted from Hongkuk Koji in parallel with water extraction and ultrasonic wave extraction. At this time, the yield of ultrasonic extract was 2~4 times higher. Thus, Monascus purpureus strains, etc. were prepared by freeze-drying powder. In conclusion, natural paints made with red pigments have enabled the development of been edible paints that can be used as eco-friendly materials with good viscosity, enhanced spread ability and coloration.

• Journal of Powder Materials
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• v.26 no.3
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• pp.195-200
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• 2019

Whisker-type magnesium hydroxide sulfate hydrate ($5Mg(OH)_2{\cdot}MgSO_4{\cdot}3H_2O$, abbreviated 513 MHSH), is used in filler and flame-retardant composites based on its hydrate phase and its ability to undergo endothermic dehydration in fire conditions, respectively. In general, the length of whiskers is determined according to various synthetic conditions in a hydrothermal reaction with high temperature (${\sim}180^{\circ}C$). In this work, high-quality 513 MHSH whiskers are synthesized by controlling the concentration of the raw material in ambient conditions without high pressure. Particularly, the concentration of the starting material is closely related to the length, width, and purity of MHSH. In addition, a ceramic-coating system is adopted to enhance the mechanical properties and thermal stability of the MHSH whiskers. The physical properties of the silica-coated MHSH are characterized by an abrasion test, thermogravimetric analysis, and transmission electron microscopy.

• Elastomers and Composites
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• v.54 no.3
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• pp.232-240
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• 2019

A superabsorbent hydrogel (SAH) can absorb and retain water weighing more than a hundred times of their dry weight because of their three-dimensional hydrophilic structure. To fabricate an SAH, itaconic acid (IA) and vinyl sulfonic acid (VSA) were subjected to radical polymerization in an aqueous solution, wherein IA and VSA were neutralized, and then, a crosslinker and a thermal initiator were added in sequence. The structure of poly(IA-co-VSA) was characterized using attenuated total reflectance Fourier-transform infrared spectroscopy. We also studied the changes in the absorption properties of the SAH composites according to the polymerization temperature, degree of neutralization, type and content of the initiator used, and type and content of the crosslinker used. Thus, we could determine the effects of some synthetic factors on the absorption properties of the SAH.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.147-156
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• 2001

Titanomagnetites, the primary magnetic mineral in submarine basalts, generally has undergone some degree of low temperature oxidation to cation-deficient titanomaghemites. Synthetic analogues of natural titanomaghemite have been prepared by the removal of iron mechanism employing a low-temperature aqueous oxidation method. Along with the low-temperature oxidation of titanomagnetite, magnetic properties of titanomagnetite change sensitively. The results show that as the degree of oxidation increases, the Curie temperature (Tc) increases from $166^{\circ}C$ to $400^{\circ}C$, saturation magnetization (Ms) at room temperature decreases from 126.30 kAlm (25.26 emu/g) to 16.55 kAlrn (3.31 emu/g) monotonously, and coercive force (Hc) and coercivity of remanence (Hcr) increase from 6.13 kAlm (77 Oe) and 23.24 kAlm (292 Oe) to 38.83 kNm (488 Oe) and 47.03 kAlm (591 Oe), respectively. Low field susceptibility (X) decreases from $2023{\times}10^{-6}SI$ to $84{\times}10^{-6}S1$. Based on the results of this study, it is interpreted that the NRM intensity variations of the oceanic crust of presetnt day to 30 Ma is due to the formation of titanomahemites of various degree of oxidation by the low-temperature aqueous oxidation of titanomagnetite, while the magnetic intensity changes of the oceanic crust older than 30 Ma is presumably caused by the combined effect of the formation of titanomaghemites and subsequent inversion of titanomagnemites. DetaileJ causes of the variations of NRM intensity of the oceanic crust may be revealed by systematic studies of the oceanic-floor basalts in the future.